1. Technical Field
The following description relates to a method of fabricating a two-terminal semiconductor component that consists of two electrodes, more specifically to a method of fabricating a semiconductor component having two terminals that can minimize the deviation in thickness during the polishing process of a semiconductor substrate and have higher reproducibility of a thinner substrate than the polishing process.
2. Description of the Related Art
Two-terminal electronic components that can be fabricated using a semiconductor include diodes, resistors, capacitors, inductors and the like. Among these, the diode is the most common active component and is employed in various circuits, such as rectifiers, oscillators and the like.
Recently, studies are underway to develop an oscillator having a high frequency band using diodes for microwaves and millimeter-waves, for example, Gunn diodes, Tunnel diodes, Impact ionization Avalanche Transit Time (IMPATT) diodes and the like.
These diodes for microwaves can convert a direct current (DC) to an alternating current (AC) by using negative differential resistance that is generated by the physical properties of a semiconductor material used for fabrication. Also, since the diodes have higher output power and lower noise characteristics than a field effect transistor (FET), these components are commonly used in circuits of an oscillator for a millimeter-wave band of 30 GHz or greater. In order to fabricate these diodes for microwaves and millimeter-waves, a semiconductor material such as gallium-arsenic (GaAs), gallium-nitride (GaN) or indium-phosphide (InP) is used. The carrier concentration and thickness of the semiconductor material may be determined according to the frequency specifications of the oscillator circuit.
Generating an alternating signal in the millimeter-wave band region generally requires the semiconductor material to have a carrier concentration of 1016 atoms per cubic centimeter (atoms/cm3) and a thickness of a few micrometers or less (1 μm=10−6 m). Used in order to fabricate these diodes for the millimeter-wave band region is a thick semiconductor substrate, on which a semiconductor material with the above-described carrier concentration and thickness is grown.
These diodes may generate a lot of heat in the materials during the operation, and the generated heat may deteriorate the properties of the components. To effectively dissipate the heat, a thinner substrate with the thickness of a few or a few tens of micrometers is used, and the diodes are adhered to a heat sink that is made of metals such as gold (Au) and copper (Cu) or materials with high thermal conductivity. The substrate is made thinner particularly for the purpose of, in addition to efficient heat dissipation, improving the property of the components by lowering series resistance of the substrate.
However, when the substrate is thinner, it is impossible to fabricate a component on the substrate, and thus GaAs or InP substrates require the thickness of 600 μm or greater for the diameter of 3 inches or greater. Thus, to make the substrate thinner, the substrate is mechanically or chemically lapped and polished. Generally, the diodes are fabricated with the thickness of 50 μm or less so as to lower the series resistance and dissipate the heat effectively.
Lapping and polishing the substrate of the thickness of 50 μm or less with the thickness deviation of 1 μm or less is a very precise and careful process. Moreover, it is not technically easy to consistently repeat the fabrication of a semiconductor component with the thickness of 50 μm or less within a minimal error range.